<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=div, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            margin: 0 auto;
            width: 24px;
            height: 20px;
            background-image: url("./images/icon.png");
            background-repeat: no-repeat;
            background-position: 0 -50px;
            border: 1px solid rgb(133, 114, 114);
            margin-bottom: 20px;
            transition: .3s linear;
        }

        .box:hover {
            background-position: 0 -74px;
        }

        .dropdown-btn {
            position: relative;
            width: 100px;
            height: 50px;
            border: 1px solid #aaa;
            line-height: 50px;
            margin: 0 auto;
            background: #ddd;
        }

        .dropdown-btn:hover {
            background: #fff;
            color: red;
        }

        .dropdown-btn:hover .dropdown-list {
            display: block;
        }

        .dropdown-list {
            position: absolute;
            top: 50px;
            left: 0;
            width: 300px;
            height: 200px;
            border: 1px solid purple;
            display: none;

        }
    </style>
</head>

<body>
    <div class="box"></div>

    <div class="dropdown-btn">
        下拉菜单
        <div class="dropdown-list"></div>
        <div>123</div>

    </div>
</body>

</html>